Fan Vertical Antenna

Discussion in 'Amateur Radio News' started by VK6FLAB, Jan 11, 2019.

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  1. W7WLL

    W7WLL Ham Member QRZ Page

    Ah, the 'fan dipole'.

    So many articles on this, including the June 2010 QST. But the oldest start of print on this antenna concept that I've found has to be the short paper by Tim Shaw of the Radio Propagation Division of the USACEEIA at Ft Huachuca AZ around '68. The title of his paper "Use of the Cobra Head to Connect Multi-Element Dipole Antennas" focuses on a Stanford Research Institute report published in '67 titled "A Field Guide To Simple H. F. Dipoles". The Shaw article principly deals with the issues of spacing between multi-element dipoles at the ends and the center.

    A second paper by Tim Shaw, titled "Multiband HF Dipoles', was found by George Lane (also of Ft Huachuca) and he published it with a cover page sometime in '72. This article delves deeper into the results of tests with a 'fan dipole'.

    Each of the articles is based on the dipoles being hung one under another, the most common form and use of a 'fan dipole' that seems to written or used. The issue of whether the center wires must be separated by X amount of space is discussed, and basically says it may or may not be advisable depending upon the end space separation of the wires.

    I recently built and installed a 40/80/160 'fan dipole' but NOT with wires one under the other. Mine is constructed closer to the QST article noted above. I use a Balun Designs 1:1 balun which from a pulley on a bracket at the top of my 70 foot crankup tower. Each side of the 40/80/160 dipoles is attached directly to the balun wire attachment supports. The dipoles run in a straight line. The ends are all at about the same height, around 30 feet at present. There is a 60 degree separation between the wires (lots of space between the ends of the wires). Looking down from the top it would look like a 6-spoke wheel but with a set of opposing spokes missing. At this point it is an experiment and I plan to do some reorientation and raising of the end heights later this coming Spring/Summer. I used the simple dipole formula and using my analyzer found the resonant point on each band to be close enough to my target point that I did not have to do any trimming. Under power the SWR at the target point is negligable, hardly visible on the meter even when running the amplifier. As one might expect the excursion up or down on 160 and to a lesser extent on 80 changes the SWR and I do have to use my ATR-30 Tuner.

    The method I used of course requires space, but if you have it makes a simple and effective low band antenna set. In spite of the terrible band conditions I've been able to pierce the East Coast RF Curtain into Europe and Africa on 40 and 80. On 160 the ambient QRN is still an issue along with poor band conditions. I beleive if I raise the ends it will be more effective. It works for me, some of you might consider something like it.

    For those not familar with Ft Huachuca, pronounce it WA Choo Ka. Back when I worked for a living, when I called on the Ft many referred to it as Ft Sneeze.

    Don W7WLL
     
    W1YW likes this.
  2. N4MIT

    N4MIT XML Subscriber QRZ Page

    WTF....
    "You might remember that I managed to drill a hole in my hand a while back"

    SMH.
     
    NH7RO, N2EY and WN1MB like this.
  3. ZL1PDT

    ZL1PDT Ham Member QRZ Page

    Yes a Fan Dipole works great and the Cobb web is based on it and have smaller foot print and you can fit it to a space at a
    small town house and have 5 bands and only 5 metes of ground for those that does not know it is 16 ft and 4 inches (16- 4" or 197")
    good luch and happy building
    Pieterm
    ZL1PDT/ Zl1PDT/ex ZS1PDT
     
  4. K4AGO

    K4AGO Ham Member QRZ Page


    You mentioned in your post "What I'm hoping to achieve is a little group of vertical antennas, connected to the same coax, mounted on the metal roof of the house...

    I seem to recall that installing an antenna on a metal (house) roof is a bad idea. Just as the antenna would not work on your metal car roof, it won't work on your metal house roof. That being said, my powers of recollection are not what they were BEFORE the onset of dementia.

    If I misspoke when I made the statement that it was a bad idea and would not work, will someone please correct my foolish statement. I honestly do not want to mislead anyone with anything I say here on the ZED.

    As far as drilling goes, may I suggest that you enlist the help of your "partner" to hold the work while you do the drilling. That way you can drill into your "partner's" hand and your hand will be no worse for the wear.

    I am reminded of a co-worker who took a karate. The first lessone he was taught was that everything in life is mind over matter. His teacher instilled the belief in him that his mind could control any and everything to prevent harm coming to him from outside forces.

    The next day he came to work and promptly showed everyone how he could keep a drill bit from going through his hand simply by using his mental capacity to make his hand so tough that the drill bit would not penetrate his hand. He then placed his hand on the drill press and pushed the pedal to the floor.

    When he held his hand up in front of his face and looked at us through the 1 1/4 inch hole through the palm of his hand, the look on his face was calssic.

    The icing on the cake was when he was discharged by Human Resources for drilling the hole through his hand. Once again, the look on his face was classic.

    Yes, Virginia, their is a Santa Claus and there is also a fool born every day.

    NO, I am not saying you are a fool; just the guy who drilled the gaping hole in his palm.

    John
    K4AGO
     
    WN1MB likes this.
  5. K2SDS

    K2SDS XML Subscriber QRZ Page

    Hah, I was waiting for your comment. I was speaking more for Onno, than others. I wouldn't want to see him get hurt again. I wish his articles would be more facts and less story telling. Maybe he should do a little research before publishing another one of his "news" articles.
     
    K4AGO likes this.
  6. W1YW

    W1YW Ham Member QRZ Page

    I'm a big fan:)
     
    NH7RO likes this.
  7. KJ4VTH

    KJ4VTH Ham Member QRZ Page

  8. AJ6O

    AJ6O Ham Member QRZ Page

    Antenna1_2_ (1).jpg Antenna2.jpg

    My monoband 40 meter, and 20 meter monoband vertical connected to the same mount. SWR is so good on both antennas no need for a tuner. Both antennas share the same feed point and radial field.
     
    KD4IEM, NH7RO, N2EY and 1 other person like this.
  9. W1YW

    W1YW Ham Member QRZ Page

    "As far as drilling goes, may I suggest that you enlist the help of your "partner" to hold the work while you do the drilling. That way you can drill into your "partner's" hand and your hand will be no worse for the wear. "

    Wise advise. The best thing I've seen, topping the OP's 'news'.

    I imagine the NEXT OP will start with... FOUNDATIONS OF ARMCHAIR RADIO

    "I was thinking that we have a monopole, and a dipole, and I thought to myself, why can't you have tripole? "

    Oh........No!
     
    Last edited: Jan 12, 2019
  10. W1YW

    W1YW Ham Member QRZ Page

    "The only fly in the ointment at this point is my unhealthy relationship with drills. You might remember that I managed to drill a hole in my hand a while back...."

    Wait...I MISSED something...is DRILLING INTO YOUR HAND a FOUNDATION OF AMATEUR RADIO?

    It MUST be important or wouldn't be part of the fireside chat...

    Yeh, I know, everyone but ME has managed to DRILL INTO THEIR HAND.

    Can we make it part of the Wouff Hong??

    I think we should do a poll: Who else has drilled into their hand?

    This is not a drill...

    Someone tell ONO not to chop onions or tomatoes or peppers in dinner prep... knives are worse than drill bits.

    Origin of HAND DRILL
    [​IMG]
     
    Last edited: Jan 12, 2019
    KK5R, NH7RO and WR2E like this.

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